Dynamic Response Analysis Of Reinforced Concrete Bridge Piers Under The Impact Of Rockfall

With the rapid development of China’s transportation industry in the western region,highways and bridges gradually extended to more remote mountainous areas,and the bridges is taking an effect that cannot be substituted for connecting the route.However,the phenomenon of rolling stones often occurs in the mountainous area due to the adverse geological conditions.So the rockfall disaster poses a serious threat to the mountain bridges.In recent years,there have been frequent incidents of Rolling Stones hitting Bridges.Then the bridge structure has been greatly damaged,and the impact of rolling stones in the mountainoud areas on the piers has gradually attracted attention.In this paper,three numerical models of bridge piers are established to analyze the dynamic response results of collision between Rolling Stones and piers with different sections.The cylindrical pier is selected as the research object,and the factors affecting the dynamic response of the pier during the impact process of the rolling stone and the pier are analyzed.The following are the main research contents and results of this article.(1)The calculation theory of the rolling stone collision problem and the finite element implementation method are introduced at home and abroad.The problems and solutions that need to be paid attention to during the numerical simulation are expounded.The finite element model of the pier,the selection of the material model and the determination of the material parameters are described in detail.(2)The numerical model of cylindrical pier,square column pier and hollow thin wall pier was established by LS-DYNA finite element software.From the impact of rolling stone,the displacement of the top and back of the pier,the equivalent stress distribution,the concrete loss ratio,the residual internal energy of the concrete,the deformation of the steel and the axial stress,the dynamic response of the three piers under the impact of the rolling stone is analyzed.The results show that the impact force of the rolling stone is greatly affected by the area of the impact contact surface and the stiffness of the pier section.The larger the impact surface area or the larger the section stiffness,the greater the impact force of the rolling stone.Equivalent stress concentration occurs at the corner near the contact area of the rolling stone of the square column pier and the hollow thin wall pier,which causes the concrete to be easily broken.Due to its structural speciality,the hollow thin-walled pier has a relatively large displacement at the top and a relatively large equivalent stress at the bottom of the pier.The bottom is prone to shear failure.(3)The cylindrical pier is selected as the research object,and the influence of the rolling stone speed,the quality of the rolling stone,the impact angle of the rolling stone and the impact position of the rolling stone on the dynamic response and failure law of the pier is further analyzed.The influence of the variation of each parameter on the pier is analyzed from the aspects of the impact force of the rolling stone,the displacement of the top and back of the pier,the concrete loss ratio and the deformation of the steel bar.The results show that the change of the speed and mass of the rolling stone has a great influence on the impact force.The greater the speed or mass,the greater the impact force of the rolling stone,the more obvious the dynamic response of the pier,the more serious the concrete damage,and the more obvious the plastic deformation of the steel bar.With the increase of the impact angle,the horizontal velocity component of the rolling stone is correspondingly reduced,and the impact on the pier is smaller.The change of the impact position of the rolling stone has no obvious influence on the dynamic response of the pier,but the closer the impact position is to the top of the pier,the greater the displacement of the top.